P0B8C is set when channel Q reports a voltage that fails the plausibility test against the other cells or the pack. On GM's 2012 two-mode trucks Q is NiMH block 17; the battery pack control module takes block 17 and block 18, multiplies each by twenty and compares with the measured pack voltage, failing beyond 70 V in 160 of 170 samples, Type B. GM's lithium-ion programs instead check that cell Q follows the average: the 2016 Volt within 7 of 8 seconds, the Cadillac ELR in 20 of 40 samples, the 2019 controllers in 35 of 40 samples with a 0.005 V trend, all Type A. Because the value itself is within limits, the driver may notice little beyond the MIL. A software update or replacement of the monitoring electronics resolves most cases.
High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
Symptoms
- MIL with little change in driving
- Usable battery capacity reduced
Most likely causes
- Monitoring electronics misreading channel Q
- Outdated battery controller software
- Block 17 or 18 voltage deviating on two-mode NiMH packs
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0B8C means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- B: Subsystem depends on the code range
- 8C: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0B8C?
If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.
What causes code P0B8C?
The most common causes are: monitoring electronics misreading channel Q; outdated battery controller software; block 17 or 18 voltage deviating on two-mode NiMH packs.
Related codes
- P0B8BHybrid/EV Battery Voltage Sense Q Circuit
- P0B8DHybrid/EV Battery Voltage Sense Q Circuit Low
- P0B8EHybrid/EV Battery Voltage Sense Q Circuit High
- P0B8FHybrid/EV Battery Voltage Sense Q Circuit Intermittent/Erratic
- P0B87Hybrid/EV Battery Voltage Sense P Circuit Range/Performance
- P0B91Hybrid/EV Battery Voltage Sense R Circuit Range/Performance
- P0ABBHybrid/EV Battery Pack Voltage Sense A Circuit Range/Performance
Sources
- gsi.ext.gm.com: 12OBDG06 Hybrid Diagnostics
- gsi.ext.gm.com: 16OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.